270 MARINE INVERTEBRATES 
Genus Petrolisthes 
P. sexspinosus. Carapace longer than broad; breadth about one 
half of an inch; space ‘between the eyes broad, but not divided into 
three teeth as in Porcellana sayana ; second joint of the cheliped has 
five broad teeth on its front edge and five or six small spines on its 
outer edge; fifth pair of legs doubled over base ‘of carapace ; whole 
body traversed with broken red lines. Found from South Carolina 
southward. (Plate LXI.) ; 
P. armatus. Carapace longer than broad; breadth about one quar- 
ter of an inch; prominent and wide between the eyes; a small sharp 
spine on each anterior side; chelipeds long; second jomt of cheliped 
twice as long as broad, with three teeth on the front edge and four or 
five small spines on the outer edge. Found on the Florida coast. 
(Plate LXI.) 
FaMILy LITHODIDE 
The species of this family have a broad, ovate, uneven body 
and a prominent rostrum. The fifth pair of legs are rudimentary 
and are folded under the carapace in the branchial chambers, so ~ 
that the crabs appear to have but four legs on each side. This is 
the distinguishing feature of the family, and makes them easily 
recognized. 
Genus Lithodes 
L. maia. The carapace is cordate (heart-shaped), and longer than 
broad, exclusive of the rostrum. The margin is recurved all around, 
and is beset with numerous very long spines. Six spines on each 
anterior side margin are regular and longer than the others. The sur- 
face of the carapace is covered with tubercles and spines and elevated 
in places. The rostrum is spiny, a third as long as the carapace, and 
has two spines atthe base, one above the other, a spine at each side, 
two lateral spines near the middle, and two terminal divergent spines. 
The chelipeds. are unequal and are covered with spines, those on the 
inner margin being the longer. The color is yellowish-red, lighter 
underneath ; the spines are darker. Found on the fishing-banks off the 
coast of Maine. (Plate LXI.) 
Genus Hehidnocerus 
E. cibarius. . This curious crab has the carapace raised in front into 
a large cone-like elevation terminating in a long point. Three promi- 
nent but smaller cones extend across the center of the back, and two still 
smaller ones occur on the posterior sides and in the middle of the poste- 
rior margin. The whole surface of the carapace is covered with coarse 
granulations arranged in rosette-like groups. The chelipeds and legs are 
beset with large tubercles and fold together in such a manner that when 
retracted the crab is a close, compact, box-like mass, with a very rough, 
